Seismic Risk Assessment for Production Scenario “Basispad Kabinet” for the Groningen field - June 2018
41
3.6
References
1.
Groningen Dynamic Model Update 2017, NAM Reservoir Engineering Team: Henk van Oeveren, Per Valvatne
and Leendert Geurtsen, September 2017.
2.
Induced Seismicity in Groningen, Assessment of Hazard, Building Damage and Risk – November 2017, NAM
(Jan van Elk and Dirk Doornhof), November 2017.
3.
Seismic risk assessment for a selection of seismic risk production scenarios for the Groningen field - Addendum
to: Induced Seismicity in Groningen Assessment of Hazard, Building Damage and Risk (November 2017), Jan
van Elk, Assaf Mar-Or, Leendert Geurtsen, Per Valvatne, Eddy Kuperus and Dirk Doornhof, March 2018.
4.
Groningen Dynamic Model Update 2017 – V5, Quint de Zeeuw, Leendert Geurtsen, September 2017.
Seismic Risk Assessment for Production Scenario “Basispad Kabinet” for the Groningen field - June 2018
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4
Event Rate and Hazard Assessment
4.1
Event Rate Forecasting
Based on the production scenarios “Basispad Kabinet”, the number of earthquakes with a magnitude larger than or
equal to M=1.5 have been forecasted. Figure 4-1 shows the annual number of earthquakes forecasted until 2032 for
Groningen field volume offtake for the “Basispad Kabinet” average temperature profile. After an initial plateau of
about 16 – 19 earthquakes per year until 2021, the seismic activity rate starts to decline. This is a consequence of
the decreasing gas production after the new nitrogen blending plant comes on stream.
Figure 4-1
Seismic Activity Rate of earthquakes for the period 2012 to 2032 (“Basispad Kabinet – Average
Temperature”). The dark grey line indicates the expected number of earthquakes in each year and the grey
area the uncertainty band.
The seismic activity rate declines to an expected 3 earthquakes per year in 2032, with an uncertainty range of 0 to 8
earthquakes per year. The seismic activity rate beyond 2025 is primarily driven by the pressure equilibration in the
field, between the high-pressure area North-West of Loppersum and the lower-pressure area South-East of the field
(Ref. 1).
The expected impact of temperature uncertainty is within the uncertainty band for event rate of the average
temperature scenario. In Figure 4-2 the seismic activity rate for three scenarios is shown; the average temperature
scenario, an average temperature scenario with gas-year 2018-2019 a cold year and an average temperature scenario
with gas-year 2018-2019 a warm year. Especially in calendar year 2019 the activity rate is higher for the cold year
scenario (20 earthquakes) than for the average temperature scenario (18 earthquakes) and lower for the warm year
scenario (15 earthquakes).
Seismic Risk Assessment for Production Scenario “Basispad Kabinet” for the Groningen field - June 2018
43
Figure 4-2
The seismic activity rate for three production scenarios; (left) the average temperature scenario, (middle) an
average temperature scenario with gas-year 2018-2019 a cold year and (right) an average temperature
scenario with gas-year 2018-2019 a warm year.
These differences in seismic activity rate between the weather scenarios are smaller than the uncertainty band for
the average weather scenario.
The seismological model is used to forecast the seismicity in terms of the number, location and magnitude of future
earthquakes. The probability of an earthquake with a magnitude exceeding a given magnitude can be assessed. In
table 4.1 the annual probability of an earthquake occurring with a magnitude exceeding the specified magnitude is
given. For instance, the probability of an earthquake occurring in 2018 with a magnitude exceeding M
L
=3.6 (the
magnitude of the Huizinge earthquake) is equal to 13%.
Year
P(M>=3.6)
P(M>=4.0)
P(M>=4.5)
P(M>=5.0)
2018
13.4%
5.5%
1.4%
0.3%
2019
14.5%
5.8%
1.3%
0.3%
2020
13.4%
5.4%
1.3%
0.3%
2021
12.2%
4.9%
1.1%
0.3%
2022
10.0%
4.0%
1.0%
0.3%
2023
7.0%
2.6%
0.7%
0.2%
2024
6.2%
2.5%
0.6%
0.2%
2025
6.0%
2.5%
0.6%
0.1%
2026
5.3%
2.2%
0.6%
0.1%
2027
4.6%
1.7%
0.4%
0.1%
Table 4.1
Table with annual probabilities for occurrence of earthquakes exceeding a set magnitude.
For comparison, the equivalent table in the “Hazard, Building Damage and Risk Assessment – November 2017” (Ref.
2) is reproduced as table 4.2. This Hazard Assessment was based on a 24 Bcm/year scenario. A reduction of the
event rate for the “Basispad Kabinet” production scenario compared to the event rate for the 24 Bcm/year scenario
can be observed. For instance, the chance of an earthquake in 2019, with a magnitude M
L
>3.6 (the magnitude of the
Huizinge earthquake in 2012), was in the report from November 2017 (Ref. 2) assessed to be 17%, based on a 24
Bcm/year production scenario. Based on “Basispad Kabinet” production scenario this chance has reduced to 14.5%.
More importantly, as a result of the declining production in the “Basispad Kabinet” scenario the chance of an
earthquake with a magnitude exceeding M
L
=3.6 (or other magnitude) is declining throughout the next 10 years.